CN115202061B - Main optical system adjustment and alignment method for large-caliber telescope - Google Patents
Main optical system adjustment and alignment method for large-caliber telescope Download PDFInfo
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- CN115202061B CN115202061B CN202210809843.0A CN202210809843A CN115202061B CN 115202061 B CN115202061 B CN 115202061B CN 202210809843 A CN202210809843 A CN 202210809843A CN 115202061 B CN115202061 B CN 115202061B
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/62—Optical apparatus specially adapted for adjusting optical elements during the assembly of optical systems
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B23/00—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices
- G02B23/02—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices involving prisms or mirrors
- G02B23/06—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices involving prisms or mirrors having a focussing action, e.g. parabolic mirror
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
- G02B7/18—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors
- G02B7/182—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors for mirrors
- G02B7/1822—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors for mirrors comprising means for aligning the optical axis
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
- G02B7/18—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors
- G02B7/182—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors for mirrors
- G02B7/183—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors for mirrors specially adapted for very large mirrors, e.g. for astronomy, or solar concentrators
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Abstract
The invention relates to the technical field of telescopes, in particular to a main optical system adjustment alignment method of a large-caliber telescope, which is used for realizing alignment of positions of a main mirror and a secondary mirror based on a secondary mirror auxiliary calibration light source and a micro-collimation telescope, and carrying out adjustment alignment of the main mirror and the secondary mirror by rotating the secondary mirror around an optimal curved surface fitting focus. Firstly, finding the optical axis of the secondary mirror when the secondary mirror is independently assembled and adjusted, placing an auxiliary calibration light source in the center of the secondary mirror, and enabling the light-emitting optical axis of the auxiliary calibration light source to be consistent with the optical axis of the secondary mirror through adjustment; then, after the secondary mirror is installed and trussed, a micro-collimation telescope is placed on a first image surface to align the secondary mirror with the center of the primary mirror, and the secondary mirror is adjusted to calibrate the light source to emit light and image at the micro-collimation telescope by adjusting the inclination of the secondary mirror; and finally, aligning the main optical system with the star, imaging a target through the detector, rotating the secondary mirror around the optimal curved surface fitting focus, and completing the coma adjustment of the main system under the condition of ensuring that the position of the secondary mirror relative to the main mirror is unchanged, thereby realizing the adjustment alignment of the main system of the foundation large-caliber telescope.
Description
Technical Field
The invention relates to the technical field of telescopes, in particular to a main optical system adjustment and alignment method of a large-caliber telescope.
Background
As the caliber of the telescope increases, the corresponding structural dimensions increase and become more and more complex, and although the overall design and processing of the optical telescope has greatly progressed, the assembly, adjustment and alignment of the main system have become important factors that restrict the improvement of the imaging performance of the foundation large caliber telescope. The alignment state of the telescope primary mirror and the telescope secondary mirror directly affects the characteristics of the telescope primary optical system, and has great influence on the overall performance of the telescope. Optical alignment refers to adjusting the attitude of an optical element so that the light wave propagates along an optimal path. The method is not only an important component for telescope installation and debugging, but also a key technology.
The premise of the assembly, adjustment and alignment of the main system is the detection of alignment errors, and the core is how to calculate the alignment errors. Research into alignment error solving methods generally needs to be performed in conjunction with a specific alignment detection light path. In addition, in order to calculate the alignment error, the alignment detection optical path may be designed according to the conditions required for the alignment error solving method. The research of telescope optical alignment method is focused more on engineering application research, so that the research is mainly performed depending on a specific optical system and according to the requirements of the specific optical system.
The existing methods for measuring the change of the optical axis are many, but are too complex. For example, 1999, luna et al proposed a method of analyzing primary and secondary mirror alignment errors using out-of-focus star images. By analyzing the relation between the inner and outer ring shapes of the defocused fixed star image of the card-type main optical system and the corresponding entrance pupil aberration, the mapping relation of the defocused fixed star image and the secondary mirror relative to the offset error of the main mirror is established. In 2011, sun Jingwei of vinca ray machine also studied an error analysis route method to solve the problem of master system adjustment. Sun Jingwei experiments show that the reflection of the inner and outer ring shapes of defocused star images on alignment errors is consistent with simulation analysis. The method has simple algorithm, and the alignment detection light path has little influence on the telescope work, so the method is a good choice for real-time alignment of astronomical telescopes. However, the alignment accuracy of this algorithm is limited and is suitable for large-scale low-accuracy alignment. In 2007, yang Haochun, wu Yun and others used the optimized function decay method to calibrate a 900 mm caliber card telescope. After two calibrations, the error of the exit pupil wavefront is 0.192 λ. The optimization function attenuation method is to measure the error of the exit pupil wavefront on the premise of establishing an optical model of the main system, establish an optimization function by taking the measured wavefront error as a target value, and treat the obtained variable value as an actual alignment error when the value of the optimization function is very close to the target value. The algorithm belongs to one of inverse optimization algorithms, has wide application, but has the defect of uncertain calculation time, and the calculation accuracy is influenced by modeling accuracy. Han Xingzi et al simulated and calibrated an optical system with an initial value of 6.7021 λ using a random gradient parallel gradient descent (SPGD) algorithm. After 200 iterations, the population of PV was reduced to 0.1967 λ. The above algorithms all belong to optimization algorithms, and the parameters of the optical system do not need to be known, and the alignment error can be directly corrected through the evaluation value representing the state of the optical system. However, the alignment state estimation function is too demanding to be able to trap into local extrema. For small caliber telescopes, the method is feasible, but for telescope systems with caliber of up to 4 meters, the height of the telescope system is up to 13m, the rear intercept is up to 56m, and the traditional method is certainly complex and difficult to realize for the adjustment and alignment of a main optical system.
Therefore, the prior art has the defect that the prior art needs to be further developed.
Disclosure of Invention
The embodiment of the invention provides a main optical system adjustment and alignment method of a large-caliber telescope, which at least solves the technical problem that an optical axis alignment and alignment method of a secondary mirror relative to a main mirror in the prior art is complex.
According to an embodiment of the present invention, there is provided a main optical system adjustment alignment method for a large caliber telescope, including the steps of:
s100: setting up a telescope system, enabling a main optical system of the telescope system to have mounting alignment adjustment, wherein the main optical system comprises a main mirror and a secondary mirror aligned with the main mirror, setting a micro-collimation telescope at a first image surface of the main optical system, and adjusting translational deviation of the secondary mirror relative to the main mirror by taking the micro-collimation telescope as a reference; the micro-collimation telescope is positioned at the first image surface position, and the image reflected by the secondary mirror on the surface of the primary mirror can be seen through the micro-collimation telescope; the first image surface is a surface of an image point position where light rays are converged through the primary mirror and the secondary mirror;
s200: according to the calibration light source placed at the center of the secondary mirror, the inclination of the secondary mirror is adjusted to realize the coincidence of the calibration light source and the optical axis of the primary mirror, so as to complete the inclination deviation adjustment of the relative position of the primary mirror and the secondary mirror;
s300: aligning the main optical system with a fixed star, rotating the main optical system according to the fixed star image acquired by the main optical system and the best fitting curved surface fitting focus around the secondary mirror, eliminating the coma influence of the main optical system by adjusting the inclination amounts of two dimensions of the secondary mirror under the condition of ensuring that the position of the secondary mirror relative to the main mirror is unchanged, and completing the adjustment and alignment of the main optical system by repeated iteration; wherein, the secondary mirror surface is a convex quadric surface, and the surface with the minimum residual error after the least square fitting is performed by fitting out a curved surface and the secondary mirror surface position deviation is the best fitting curved surface.
Further, when the main optical system is aligned to the star, based on the star image acquired by the main optical system, the main optical system rotates around the best curved surface fitting focus according to the secondary mirror, and under the condition that the position of the secondary mirror relative to the main mirror is unchanged, the coma influence of the main optical system is eliminated, and after the adjustment and alignment of the main optical system are completed through repeated iteration, the method further comprises the steps of:
and detecting whether the optical axis alignment of the secondary mirror and the main mirror meets the requirement, and if the optical axis alignment of the secondary mirror and the main mirror does not meet the requirement, repeating the steps S100-S300 until the optical axis alignment of the secondary mirror and the main mirror meets the requirement.
Further, a telescope system is built, a main optical system of the telescope system is provided with an installation alignment adjustment, the main optical system comprises a main mirror and a secondary mirror aligned with the main mirror, an imaging detector is arranged at a first phase surface of the main optical system, and translational deviation of the secondary mirror relative to the main mirror is specifically adjusted by taking a micro collimation telescope as a reference:
constructing a telescope system, wherein the telescope system comprises a main optical system, and the main optical system comprises a primary mirror and a secondary mirror;
setting a calibration light source at the center of the secondary mirror;
setting a microcollimator telescope on a first image plane of a main system;
and adjusting the two-dimensional translation of the secondary mirror relative to the primary mirror by taking the microcollimator telescope as a reference.
Further, aligning the main optical system with the star, rotating the main optical system around the best curved surface fitting focus according to the secondary mirror based on the star image acquired by the main optical system, eliminating the coma influence of the main optical system under the condition of ensuring that the secondary mirror is unchanged relative to the main mirror, and completing the adjustment and alignment of the main optical system by repeated iteration specifically comprises:
setting an imaging detector at a preset position of a first image surface of a main optical system, adjusting a preset value of a focal length value of a secondary mirror relative to the position of the main mirror, and aligning the main optical system with a fixed star target to obtain a fixed star image;
moving the imaging detector by a preset distance to enable the star image to be in a defocusing state;
performing closed-loop tracking on a fixed star target, adjusting the pointing direction of a telescope system to enable a defocused fixed star image to be positioned at the center of a view field of the telescope system, calculating contour lines of inner and outer edges generated by the defocused fixed star image, and calculating a conversion matrix of the calculated coordinate system and a calibration coordinate system; the calculated coordinate system is a star imaging coordinate system acquired by the telescope system, and the calibrated coordinate system is a coordinate system in the adjustment process of the main optical system;
calculating corresponding component delta L of eccentric quantity of inner and outer rings of defocused star image in x-axis and y-axis x 、ΔL y And the ratio of the lengths of the x axis and the y axis of the inner ring and the outer ring of the star image, and the alignment errors delta h and delta theta of the secondary mirror are calculated according to the alignment errors of the star image; wherein, the x-axis coordinate system and the y-axis coordinate system are the calculated coordinate system;
rotating according to the best curve fitting focus of the secondary mirror, and calculating the corresponding component delta L of the eccentric quantity of the inner ring and the outer ring of the defocused star image in the x-axis and the y-axis in real time based on the star image acquired in the imaging detector x 、ΔL y And the ratio of the lengths of the x axis and the y axis of the inner ring and the outer ring of the star image respectively, is delta L x 、ΔL y And when the ratio of the lengths of the x axis to the y axis of the inner ring and the outer ring is minimum, eliminating the coma influence of the main optical system, and finishing the adjustment and the alignment of the main optical system through repeated iteration.
Further, setting an imaging detector at a preset position of a first image plane of the primary optical system, adjusting a preset value of a focal length value of the secondary mirror relative to the position of the primary mirror, and aligning the primary optical system with a star target to obtain a star image includes:
and acquiring a fixed star image by adjusting the interval between the primary mirror and the secondary mirror so as to acquire a defocused image of the fixed star image.
Further, the telescope system comprises a turntable, a four-way structure, a truss and a ring beam, wherein the four-way structure is arranged on the turntable, the truss is arranged on the four-way structure and supports the ring beam, the secondary mirror is arranged on the ring beam, the primary mirror is arranged on one side, far away from the primary mirror, of the four-way structure, and the secondary mirror and the primary mirror are aligned.
Further, a six-degree-of-freedom platform is arranged on the ring beam, and the secondary mirror is arranged on the six-degree-of-freedom platform.
Further, a main mirror chamber is arranged on the turntable, the main mirror chamber is positioned at one side of the four-way structure far away from the secondary mirror, and the host is arranged in the main mirror chamber.
According to the main optical system adjustment alignment method of the large-caliber telescope, the alignment of the positions of the main mirror and the secondary mirror is realized based on the secondary mirror auxiliary calibration light source and the micro-collimation telescope, and the main mirror and the secondary mirror are adjusted and aligned by rotating the secondary mirror around the optimal curved surface fitting focus. Firstly, finding the optical axis of the secondary mirror when the secondary mirror is independently assembled and adjusted, placing an auxiliary calibration light source in the center of the secondary mirror, and enabling the light-emitting optical axis of the auxiliary calibration light source to be consistent with the optical axis of the secondary mirror through adjustment; then, after the secondary mirror is installed and trussed, a micro-collimation telescope is placed on a first image surface to align the secondary mirror with the center of the primary mirror, and the secondary mirror is adjusted to calibrate the light source to emit light and image at the micro-collimation telescope by adjusting the inclination of the secondary mirror; and finally, aligning the main optical system with the star, imaging a target through the detector, rotating the secondary mirror around the optimal curved surface fitting focus, and completing the coma adjustment of the main system under the condition of ensuring that the position of the secondary mirror relative to the main mirror is unchanged, thereby realizing the adjustment alignment of the main system of the foundation large-caliber telescope.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and together with the description serve to explain the invention and do not constitute a limitation on the invention. In the drawings:
FIG. 1 is a flow chart of a main optical system adjustment alignment method of a large caliber telescope of the present invention;
FIG. 2 is a flow chart of an embodiment of the main optical system alignment procedure of the large caliber telescope according to the present invention;
FIG. 3 is a diagram of the definition of the alignment error of the primary optical system of the present invention;
FIG. 4 is a schematic view of a primary optical system of a 4-meter grade foundation telescope according to an embodiment of the present invention;
FIG. 5 is a graph showing the translational misalignment of the secondary mirror relative to the primary mirror in accordance with the present invention;
fig. 6 is a schematic diagram of an out-of-focus star image according to the present invention.
Detailed Description
In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
Aiming at a telescope system with caliber of 4m, the height of the telescope system reaches 13m, the rear intercept reaches 56m, and the traditional method is complex and difficult to realize for the adjustment and alignment of a main optical system. Based on the existing defects, the invention provides a primary and secondary mirror alignment method based on secondary mirror auxiliary calibration light source and first image surface placed micro-collimation telescope.
Aiming at the problem that a primary optical system of the foundation large-caliber telescope is difficult to construct a collimation light path through an interferometer and a plane mirror in practical engineering application, the invention provides a primary and secondary mirror position alignment method based on secondary mirror auxiliary calibration light source and a first image surface placement microcollimator telescope, and the primary and secondary mirror adjustment alignment method is carried out by rotating a secondary mirror around an optimal curved surface fitting focus so as to meet the use requirement of the primary optical system of the foundation large-caliber telescope.
For large caliber telescopes, the primary mirror is generally heavy, and the supporting and adjusting mechanism of the primary mirror is complex, so that the primary mirror is difficult to adjust. Meanwhile, the adjustment of the main mirror can cause deviation of the optical axis and the visual axis, visual field deviation and the like, and when the main mirror reaches 4m caliber, the mirror surface support of the main mirror is realized in an active support mode, so that the main mirror has a main mirror position detection function, and the space position of the main mirror can be ensured to be unchanged in real time. Compared with the main mirror, the secondary mirror has the advantages of light weight, simple structure, convenient adjustment, unchanged view field and the like. Thus, the alignment error of the primary and secondary mirrors is caused by the variation of the secondary mirror, i.e. there is an alignment error of the secondary mirror with respect to the primary mirror. Only the rigid bodies of the primary mirror and the secondary mirror are discussed herein, the cartesian rectangular coordinate system is established by taking the vertex of the working surface of the primary mirror as the origin of coordinates and the optical axis of the primary mirror as the Z axis, and the definition of the alignment error of the primary optical system is shown in fig. 3. The displacement of the secondary mirror relative to the primary mirror in FIG. 3 is h 1 The secondary mirror has a tilt θ relative to the primary mirror 1 。
After the main mirror, the main mirror chamber, the secondary mirror, the supporting structure and the truss are connected to form an independent component, the main mirror and the secondary mirror component are assembled together to form a main optical system, and the main optical system is assembled, adjusted and aligned to adjust the eccentric error delta h of the optical axis of the secondary mirror relative to the main mirror 1 Tilt error Δθ 1 And defocus errors are adjusted to a minimum. Although the alignment errors have a characteristic of compensating each other, the optimal image quality cannot be obtained, and the pointing accuracy is affected. In order to optimize imaging quality and pointing accuracy, the decentration error, tilt error, and defocus error must be corrected simultaneously. Thus, the secondary mirror is neededMultidimensional adjustment is performed. The principal optical system diagram of the 4 m-level foundation telescope herein is shown in fig. 4.
Although the reasons for the relative deviation of each primary mirror and each secondary mirror can be analyzed, the change rule and the magnitude of the alignment deviation of the primary system caused by the superposition of all influencing factors in the assembling process of the telescope are quite complex. The invention discloses a primary and secondary mirror alignment method based on secondary mirror auxiliary calibration light source and a primary image surface placed micro-collimation telescope, which is used for realizing primary and secondary mirror position alignment.
Referring to fig. 1 and 2, according to an embodiment of the present invention, there is provided a main optical system adjustment alignment method for a large caliber telescope, including the steps of:
s100: setting up a telescope system, enabling a main optical system of the telescope system to have mounting alignment adjustment, wherein the main optical system comprises a main mirror and a secondary mirror aligned with the main mirror, setting a micro-collimation telescope at a first image surface of the main optical system, and adjusting translational deviation of the secondary mirror relative to the main mirror by taking the micro-collimation telescope as a reference; the micro-collimation telescope is positioned at the first image surface position, the image reflected by the secondary mirror on the surface of the primary mirror can be seen through the micro-collimation telescope, and fig. 5 is the image seen by the micro-collimation telescope, and the effect of the micro-collimation telescope is that the relative position relation between the primary mirror and the secondary mirror can be accurately measured; the first image plane is a plane at the position of an image point where light rays are converged after passing through the primary mirror and the secondary mirror.
S200: according to the calibration light source placed at the center of the secondary mirror, the inclination of the secondary mirror is adjusted to realize the coincidence of the calibration light source and the optical axis of the primary mirror, so as to complete the inclination deviation adjustment of the relative position of the primary mirror and the secondary mirror;
s300: aligning a main optical system with a fixed star, rotating the main optical system according to a fixed star image acquired by the main optical system and around a best fitting curved surface fitting focus according to a secondary mirror, eliminating the coma influence of the main optical system by adjusting the inclination amounts of two dimensions of the secondary mirror under the condition of ensuring that the position of the secondary mirror relative to the main mirror is unchanged, and completing the adjustment and alignment of the main optical system by repeated iteration; the secondary mirror surface is a convex quadric surface, and the surface with the minimum residual error after the least square fitting is carried out on a curved surface and the secondary mirror surface position deviation through fitting is the best fit curved surface.
Specifically, the secondary mirror surface is a convex quadric surface, and the surface with the minimum residual error after the least square method fitting is performed on a curved surface and the secondary mirror surface position deviation in the calculation simulation process is the best fitting curved surface. The surface vertex of the best fit curved surface is consistent with the position of the secondary mirror center vertex.
Specifically, for the main optical system with a classical cassegrain Lin Fanshe type structure, coma aberration of the main system can be eliminated by adjusting the inclination amounts of two dimensions of the secondary mirror in the adjustment process.
According to the main optical system adjustment alignment method of the large-caliber telescope, the alignment of the positions of the main mirror and the secondary mirror is realized based on the secondary mirror auxiliary calibration light source and the micro-collimation telescope, and the main mirror and the secondary mirror are adjusted and aligned by rotating the secondary mirror around the optimal curved surface fitting focus. Firstly, finding the optical axis of the secondary mirror when the secondary mirror is independently assembled and adjusted, placing an auxiliary calibration light source in the center of the secondary mirror, and enabling the light-emitting optical axis of the auxiliary calibration light source to be consistent with the optical axis of the secondary mirror through adjustment; then, after the secondary mirror is installed and trussed, a micro-collimation telescope is placed on a first image surface to align the secondary mirror with the center of the primary mirror, and the secondary mirror is adjusted to calibrate the light source to emit light and image at the micro-collimation telescope by adjusting the inclination of the secondary mirror; and finally, aligning the main optical system with the star, imaging a target through the detector, rotating the secondary mirror around the optimal curved surface fitting focus, and completing the coma adjustment of the main system under the condition of ensuring that the position of the secondary mirror relative to the main mirror is unchanged, thereby realizing the adjustment alignment of the main system of the foundation large-caliber telescope.
From the general flow, the main optical system adjustment alignment process includes the following three steps:
the first step: after the whole telescope is built, the telescope is provided with a main optical system adjustment alignment condition, and the translational deviation delta h of the secondary mirror relative to the main mirror is adjusted by taking the micro-collimation telescope at the first top surface as a reference 1 As shown in fig. 5.
And a second step of: and placing a calibration light source according to the center position of the secondary mirror, and adjusting the inclination of the secondary mirror to realize the coincidence of the calibration light source and the optical axis of the primary mirror, thereby completing the inclination deviation adjustment of the relative position of the primary mirror and the secondary mirror.
And a third step of: and rotating according to the best curve fitting focus of the secondary mirror, eliminating the coma influence of the main optical system based on the fixed star image in the imaging detector at the first image plane, and completing the adjustment and the pairing of the main optical system of the telescope through repeated iteration.
The step S300 specifically includes:
in the actual adjustment process, the optical parameters of the secondary mirror are designed to be known quantities, and the incident light of the star is considered to be always parallel to the optical axis of the main optical system. The alignment error is calculated using the center deviation Δl of the inner and outer rings due to the secondary mirror center obscuration of the defocused star image and the length ratio of the respective x-axis and y-axis of the inner and outer rings, as shown in fig. 6. In the actual operation process, due to the existence of factors such as pointing error, tracking error, position error of an image detector and the like, whether the star image is strictly parallel to the optical axis of the main system or not cannot be judged, and because the field of view of the main optical system is 3', the influence of the change in the field of view on the shape of the inner ring and the outer ring generated by the defocused star image can be ignored.
Step S300 is described in detail below:
step one: the imaging detector is fixed near the theoretical position, the secondary mirror is adjusted along the z-axis to focus relative to the primary mirror, so that the spot diameter of the star image is minimized, and the imaging detector can be judged by observing the energy concentration of darker stars. Generally, when the energy of the darker stars is concentrated most, the position is the best imaging surface. At this time, the secondary mirror position is considered to be close to the theoretical value.
Step two: the imaging detector and the secondary mirror adjusting mechanism coordinate system are calibrated.
Step three: the imaging detector is moved by a distance delta L to enable the target image to be in a defocusing state, the defocusing amount is set based on the fact that the inner ring and the outer ring generated by the defocusing star image can be distinguished obviously, and the exposure time is required to be increased in the actual adjustment process so as to obtain the optimal sampling image.
Step four: and (3) carrying out closed-loop tracking on the fixed star target, adjusting the pointing direction of the telescope to enable the defocused fixed star image to be positioned at the center of the field of view, calculating the contour lines of the inner edge and the outer edge generated by the defocused fixed star image, and calculating a conversion matrix of the calculated coordinate system and the calibrated coordinate system. The calculation coordinate system is a star imaging coordinate system acquired by the telescope system, and the calculation coordinate system is a coordinate system of a star imaging on a camera target surface of the telescope; the calibration coordinate system is a coordinate system in the adjustment process of the main optical system; because the imaging target surface is of a fixed size, the center of the field of view of the target surface can be found by means of image finding elements.
Step five: calculating the component delta L of the eccentric quantity of the inner ring and the outer ring of the defocused star image in the x-axis and the y-axis x 、ΔL y And the ratio of the lengths of the x axis and the y axis of the inner ring and the outer ring respectively, and calculating the alignment errors delta h and delta theta of the secondary mirror according to an alignment error solving algorithm utilizing the defocused fixed star image. The x-axis coordinate system and the y-axis coordinate system are the calculated coordinate system, and the coordinate system is established according to the target surface position.
Step six: rotating according to the best curve fitting focus of the secondary mirror, and calculating the component delta L of the eccentric quantity of the inner ring and the outer ring of the defocused fixed star image in the x axis and the y axis in real time based on the fixed star image in the imaging detector at the first image plane x 、ΔL y And the ratio of the lengths of the X axis and the Y axis of the inner ring and the outer ring respectively, is delta L x 、ΔL y And eliminating the coma influence of the main optical system when the ratio of the lengths of the x axis to the y axis of the inner ring and the outer ring is minimum.
After step S300, the method further comprises:
and detecting whether the optical axis alignment of the secondary mirror and the main mirror meets the requirement, and if the optical axis alignment of the secondary mirror and the main mirror does not meet the requirement, repeating the steps S100-S300 until the optical axis alignment of the secondary mirror and the main mirror meets the requirement. After the secondary mirror and the primary mirror are aligned and adjusted, the alignment effect can be detected to see whether the requirements are met. The requirement may be whether the overlap ratio of the optical axis of the secondary mirror and the optical axis of the primary mirror reaches a preset value; the requirements can also be met by whether the star images seen by the secondary mirror and the primary mirror after adjustment meet the requirements of the acquired images, such as whether the stars of shooting motions have tails or not, and if not, the requirements are met.
In the embodiment, since the on-site image detector is fixed and is inconvenient to adjust, the out-of-focus image acquisition of the star image is realized by adjusting the interval between the primary mirror and the secondary mirror, so that the actual parameter and the theoretical parameter can be changed. However, since the telescope is a coaxial telescope, the calculation error caused by the linearity error in the secondary mirror defocusing process has little influence on the calculation accuracy of the adjustment and alignment error of the main optical system when the z-axis deviation amount is small, and the situation of inversion does not occur.
Referring to fig. 4, the telescope system includes a turntable, a four-way structure, a truss and a ring beam, the four-way structure is disposed on the turntable, the truss is disposed on the four-way structure and supports the ring beam, a secondary mirror is disposed on the ring beam, a primary mirror is disposed on a side of the four-way structure away from the primary mirror, and the secondary mirror is aligned with the primary mirror. The ring beam is in a ring shape, the secondary mirror is arranged at the center of the ring beam, the primary mirror is aligned with the secondary mirror at one side of the four-way structure far away from the secondary mirror, and the secondary mirror can be adjusted on the ring beam.
In an embodiment, the ring beam is provided with a six-degree-of-freedom platform, and the secondary mirror is arranged on the six-degree-of-freedom platform. The secondary mirror adjusts the alignment position of the secondary mirror by the six-degree-of-freedom stage according to the six-degree-of-freedom stage.
In the embodiment, a main mirror chamber is arranged on the turntable, the main mirror chamber is positioned at one side of the four-way structure far away from the secondary mirror, and the host is arranged in the main mirror chamber. The primary mirror is positioned in the primary mirror chamber to increase the stability of the primary mirror.
The invention has the remarkable advantages that the invention can provide an adjustment scheme with extremely high feasibility for the main optical system adjustment alignment of a large foundation telescope, creatively provides a method for carrying out the alignment adjustment of the main optical system based on the rotation of the best curve fitting focus of the secondary mirror, ensures that the pointing direction of the telescope is not changed while the main optical system alignment process of the telescope is carried out, ensures that the tracking pointing precision of the telescope reaches the optimal state, and has higher application value and innovation compared with the traditional method.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (7)
1. The main optical system adjustment and alignment method of the large caliber telescope is characterized by comprising the following steps:
s100: setting up a telescope system, and enabling a main optical system of the telescope system to have mounting alignment adjustment, wherein the main optical system comprises a main mirror and a secondary mirror aligned with the main mirror, a micro-collimation telescope is arranged at a first image surface of the main optical system, and translational deviation of the secondary mirror relative to the main mirror is adjusted by taking the micro-collimation telescope as a reference; the micro-collimation telescope is positioned at the first image surface position, and the image reflected by the secondary mirror on the surface of the primary mirror can be seen through the micro-collimation telescope; the first image plane is a plane of an image point position where light rays are converged after passing through the primary mirror and the secondary mirror;
s200: according to the calibration light source placed at the center of the secondary mirror, the inclination of the secondary mirror is adjusted to realize the superposition of the calibration light source and the optical axis of the primary mirror, so that the inclination deviation adjustment of the relative position of the primary mirror and the secondary mirror is completed;
s300: setting an imaging detector at the first image plane; aligning the primary optical system with a star, rotating the primary optical system around a best fitting curved surface fitting focus according to the secondary mirror based on a star image acquired by the primary optical system, eliminating the coma influence of the primary optical system by adjusting the inclination amount of two dimensions of the secondary mirror under the condition of ensuring that the position of the secondary mirror relative to the primary mirror is unchanged, and completing the adjustment and alignment of the primary optical system by repeated iteration;
the secondary mirror surface is a convex quadric surface, and the surface with the minimum residual error after least square fitting is carried out on a curved surface and the secondary mirror surface position deviation by fitting is the best fit curved surface;
the step S300 specifically includes:
setting an imaging detector at a preset position of a first image plane of the main optical system, adjusting a preset value of a focal length value of the secondary mirror relative to the position of the main mirror, and aiming the main optical system at a star target to obtain a star image;
moving the imaging detector by a preset distance to enable the star image to be in a defocusing state;
performing closed-loop tracking on the star target, adjusting the pointing direction of the telescope system to enable the defocused star image to be positioned at the center of a view field of the telescope system, calculating contour lines of inner and outer edges generated by the defocused star image, and calculating a conversion matrix of a calculation coordinate system and a calibration coordinate system; the calculated coordinate system is a star imaging coordinate system acquired by the telescope system, and the calibrated coordinate system is a coordinate system in the adjustment process of the main optical system;
calculating the corresponding component of the eccentric quantity of the inner ring and the outer ring of the star image in the x-axis and the y-axis
、/>
And the ratio of the lengths of the x axis and the y axis of the inner ring and the outer ring of the star image, the alignment error of the secondary mirror is calculated according to the alignment error of the star image
、/>
The method comprises the steps of carrying out a first treatment on the surface of the Wherein, the x-axis coordinate system and the y-axis coordinate system are the calculated coordinate system; />
Is the eccentric error of the optical axis of the secondary mirror relative to the main mirror,
Is the tilt error of the minor optical axis relative to the major mirror;
rotating according to the best curve fitting focus of the secondary mirror to obtain the final productReal-time calculating components of the eccentric amount of the inner ring and the outer ring of the out-of-focus star image corresponding to the x axis and the y axis according to the star image acquired in the imaging detector
、/>
And the ratio of the lengths of the x and y axes of the inner and outer rings of the sun image, respectively, is within the +.>
、/>
And when the ratio of the lengths of the x axis to the y axis of the inner ring and the outer ring is minimum, eliminating the coma influence of the main optical system, and finishing the adjustment and the alignment of the main optical system through repeated iteration.
2. The method of aligning the main optical system of a large caliber telescope according to claim 1, further comprising, after step S300:
and detecting whether the optical axis alignment of the secondary mirror and the main mirror meets the requirement, and if the optical axis alignment of the secondary mirror and the main mirror does not meet the requirement, repeating the steps S100-S300 until the optical axis alignment of the secondary mirror and the main mirror meets the requirement.
3. The method for adjusting and aligning a main optical system of a large caliber telescope according to claim 1, wherein the telescope system is built, and the main optical system of the telescope system is provided with an adjusting and aligning adjustment, the main optical system comprises a main mirror and a secondary mirror aligned with the main mirror, a micro-collimating telescope is arranged at a first image plane of the main optical system, and a translational deviation of the secondary mirror relative to the main mirror is adjusted based on the micro-collimating telescope, specifically:
building the telescope system, wherein the telescope system comprises the main optical system, and the main optical system comprises a primary mirror and a secondary mirror;
setting the calibration light source at the center of the secondary mirror;
setting the microcollimator telescope on a first image plane of the main optical system;
and adjusting the two-dimensional translation of the secondary mirror relative to the primary mirror by taking the microcollimator telescope as a reference.
4. The method according to claim 1, wherein the setting an imaging detector at a preset position of a first image plane of the main optical system, adjusting a preset value of a focal length value of the secondary mirror relative to the position of the main mirror, and aligning the main optical system with a star target to obtain a star image, comprises:
and acquiring the star image by adjusting the interval of the primary mirror and the secondary mirror so as to acquire the defocused image of the star image.
5. The method of claim 1, wherein the telescope system comprises a turntable, a four-way structure, a truss and a ring beam, the four-way structure is arranged on the turntable, the truss is arranged on the four-way structure and supports the ring beam, the secondary mirror is arranged on the ring beam, the primary mirror is arranged on one side of the four-way structure far from the primary mirror, and the secondary mirror is aligned with the primary mirror.
6. The method of aligning a main optical system of a large caliber telescope according to claim 5, wherein the ring beam is provided with a six-degree-of-freedom platform, and the secondary mirror is provided on the six-degree-of-freedom platform.
7. The method of adjusting and aligning a main optical system of a large caliber telescope according to claim 6, wherein a main mirror chamber is provided on the turntable, the main mirror chamber is located at a side of the four-way structure away from the secondary mirror, and the main mirror is provided in the main mirror chamber.
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| CN116699864B (en) * | 2023-07-31 | 2023-10-20 | 中国科学院长春光学精密机械与物理研究所 | Reference-free adjustment method, device, equipment and medium for space-based large optical system |
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| CN207689740U (en) * | 2017-09-21 | 2018-08-03 | 安徽蓝盾光电子股份有限公司 | A kind of device improving FTIR transmitter unit emergent light light intensity |
| CN108957726B (en) * | 2018-06-29 | 2021-03-05 | 中国科学院国家天文台 | Quick adjusting method for axisymmetric telescope by taking image plane as reference |
| CN112946852B (en) * | 2021-03-24 | 2023-04-11 | 中国科学院西安光学精密机械研究所 | Primary and secondary mirror system adjustment method |
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